[amelia] Error message

Hi there, I am new to MI and was wondering if I could obtain some help. At the moment, I am performing MI on a dataset of size n= 200. This appears to work fine. However, part of my project is to break up the data set into male (n=92) and female (n=108). When I try and run the same MI for the male and female data sets using the Ameila package, I get the following errors For the male data set, the error message: "The resulting variance matrix was not invertible. Please check your data for highly collinear variables. Warning message: In amelia.prep(data = data, m = m, idvars = idvars, empri = empri, : You have a small number of observations, relative to the number, of variables in the imputation model. Consider removing some variables," and for the female data set: "The resulting variance matrix was not invertible. Please check your data for highly collinear variables." As a result, if I want to perform m = 50 imputations, R will only provide me with 40 or so. Have others had similar problems? If so how have you overcome them. If not, what can you suggest I do? Regards, Ian - Amelia mailing list served by Harvard-MIT Data Center [Un]Subscribe/View Archive: http://lists.gking.harvard.edu/?info=amelia